Answer:
9 cm
Step-by-step explanation:
[tex]\boxed{\begin{minipage}{4.5 cm}\underline{Area of a square}\\\\$A=s^2$\\\\where:\\ \phantom{ww}$\bullet$ $A$ is the area\\ \phantom{ww}$\bullet$ $s$ is the side length\\\end{minipage}}[/tex]
Given:
Substitute the given values into the formula:
[tex]\implies 81=c^2[/tex]
[tex]\implies \sqrt{c^2}=\sqrt{81}[/tex]
[tex]\implies c=9[/tex]
Therefore, the side length of the square is 9 cm.
